The present invention relates generally to thermal-aerosol generating methods and apparatus and more particularly to the structure and use of an improved thermal-aerosol generator having a quick change pressurized fog and/or smoke producing material container and to a method of employing such a thermal-aerosol generator to test for openings in regions such as sewers, pipes or boilers and similar conduits or containers, including new sewer line construction before backfilling.
The infiltration of unwanted surface and storm water into sewers and particularly sanitary sewer systems is costly with one estimate being that at least 15 percent of the total capacity of the sanitary sewer systems nationwide is lost due to the presence and infiltration of such surface and storm water which, once introduced into the sanitary sewer system, must be processed with the normal sanitary sewage. A substantial cost savings is available by eliminating such surface water infiltration and an economical and effective process for locating, determining and/or pinpointing the points of inflow or infiltration of such surface or storm water, followed by the elimination of such inflow or infiltration points is highly desirable. With the advent of Federal legislation limiting the ingress of surface and/or storm run-off water into sanitary sewage treatment systems, this locating, determining, pinpointing and eliminating of such points has become essential. Over 60 percent of such surface water intrusion occurs through laterals and house plumbing. Smoke tests reveal the following faults:
(1) Leaks permitting surface infiltration;
(2) Connected roof and cellar drains;
(3) Connected sanitary and storm sewers;
(4) All connected lines, including abandoned and supposedly unconnected lines;
(5) Leaky manholes;
(6) Uncapped lines;
(7) Lost manholes;
(8) Unmetered connections where meters are required;
(9) Rodent passages leading into lines.
The smoke-testing of sanitary sewers to locate illegal inflow or infiltration has been attempted but with little real degree of completeness or total sucess of such operations.
To perform such a smoke-test, a section or region of the sanitary sewer or the like is isolated, for example, by placing bags of sand or small rocks or other obstructions or inflatable plugs at two or more locations to isolate the region. A somewhat centrally located sanitary sewer or the like manhole cover is removed and replaced by an apertured piece of plywood or the like and the smoke is introduced through the aperture to the system, and points at which that smoke escapes are identified for corrective action, if necessary. A partially filled innertube, tire flap or other sealing device is sometimes employed intermediate the plywood and pavement or other surface for sealing purposes.
The actual smoke generation is accomplished by placing a smoke candle or smoke bomb at the intake of a small portable blower, the output of which is coupled to the plywood aperture. Typically, several such smoke bombs are required to adequately test a reasonable size sewer region. The emergence of smoke from a residential vent pipe for example, is normal and does not indicate an illegal connection, however, smoke rising from residential downspouts or outside drains and catch basins does indicate an illegal connection which in the aggregate can be highly detrimental to the sanitary sewage system capacity.
Other attempts to identify improper water inlets to such systems have included the closed circuit television inspection or even photographing of the pipe interior as well as low pressure air testing, where a region is pressurized slightly, and the time rate of decrease of that pressure measured to determine the amount but not the location of improper openings. Also the flow rate of water throughout the system may be monitored to determine where excess flows exist.
It is also known in the prior art, as exemplified by my prior U.S. Pat. No. 3,607,780, to generate a voluminous fog and/or smoke by thermal-aerosol principles. In the device of my patent, an insecticide, riot control agent including smoke or other fog and/or smoke producing material, is supplied to an exhaust manifold and mixed with and atomized and vaporized by the exhaust gases emanating from an internal combustion engine, and the atomized and vaporized material-exhaust gas mixture is conduited to the output of a blower driven by the same engine so as to disperse the agent as a fog and/or smoke. Such a thermal-aerosol approach does not employ pyrotechnic devices, such as smoke bombs or smoke candles thereby minimizing any danger from fire and explosion, and as compared to a smoke bomb or smoke candle approach, minimizes the exposure of the machine to the fog or smoke producing agent by introducing that fog and/or smoke product at the blower outlet, rather than the blower inlet, as with, for example, a smoke bomb. Further, while a smoke bomb must be allowed to run or burn its course, extremely short applications of fog and/or smoke are available from a thermal-aerosol generator, and for extremely long applications of smoke, several smoke bombs are required, while only one or at most just a very few canisters of fog and/or smoke producing material are required with a thermal-aerosol generator. About a dozen commercially available smoke bombs are required to equal the volume and density of smoke or fog available from a single container according to the present invention. A smoke bomb and the prior art thermal-aerosol generators provide an interrupted flow of smoke or fog when such sources are changed, however, with the present invention, as will appear more clearly subsequently, an uninterrupted flow of fog and/or smoke of controllable density and volume is possible. It should also be noted that the materials used in smoke bombs and smoke candles create a smoke which is at least somewhat toxic and at least somewhat corrosive.